Liverpool dominated from the off, and they were rewarded midway through the first half when Alexander-Arnold curled an exceptional free-kick into the back of the net.
Salah, who missed the Reds' draw at Goodison Park on Sunday, made it two just before the break as he got in behind the visitors' defence and finished with confidence.
Jurgen Klopp's side then went 3-0 ahead through a stunning long-range strike from Fabinho, before Sadio Mane rounded off an excellent move between the front-three to make it four.
The result sees Liverpool on the cusp of winning the Premier League title, which they could do as early as tomorrow night.
Should Manchester City drop points away to Chelsea, the Reds would be crowned champions for the first time in 30 years. But if Pep Guardiola's side come out on top, the Reds can then finish the job against them on 2 July.
Slide through our gallery below for all the best snaps from Anfield on Wednesday night.